CoFe-LDH nanowire arrays on graphite felt: A high-performance oxygen evolution electrocatalyst in alkaline media

Developing non-noble-metal oxygen evolution reaction(OER) electrocatalysts with high performance is critical to electrocatalytic water splitting. In this work, we fabricated Co Fe-layered double hydroxide(LDH) nanowire arrays on graphite felt(Co Fe-LDH/GF) via a hydrothermal method. The Co Fe-LDH/GF, as a robust integrated 3 D OER anode, exhibits excellent catalytic activity with the need of low overpotential of 252 and 285 mV to drive current densities of 10 and 100 mA/cm^(2) in 1.0 mol/L KOH, respectively. In addition, it also maintains electrochemical durability for at least 24 h. This work would open up avenues for the development of GF like attractive catalyst supports for oxygen evolution applications.

In situ grown Fe_(3)O_(4)particle on stainless steel:A highly efficient electrocatalyst for nitrate reduction to ammonia

NH_(3)is an essential feedstock for fertilizer synthesis.Industry-scale NH_(3)synthesis mostly relies on the Haber-Bosch method,however,which suffers from massive CO_(2) emission and high energy consumption.Electrocatalytic NO_(3)-reduction is an attractive substitute to the Haber-Bosch method for synthesizing NH_(3)under mild conditions.As this reaction will produce a variety of products,it highly desires efficient and selective electrocatalyst for NH_(3)generation.Here,we report in situ grown Fe_(3)O_(4)particle on stainless steel(Fe_(3)O_(4)/SS)as a high-efficiency electrocatalyst for NO_(3)^(-)reduction to NH_(3).In 0.1 M NaOH with 0.1 M NaNO_(3),such Fe_(3)O_(4)/SS reaches a remarkable Faradaic efficiency of 91.5%and a high NH_(3)yield of 10,145μg·h^(-1)·cm^(-2)at-0.5 V vs.reversible hydrogen electrode(RHE).Furthermore,it owns robust structural and electrochemical stability.This work provides useful guidelines to expand the scope of metallic oxide electrocatalysts for NH_(3)synthesis.The catalytic mechanism is uncovered and discussed further by theoretical calculations.

Ambient ammonia production via electrocatalytic nitrite reduction catalyzed by a CoP nanoarray

Industrial-scale ammonia(NH_(3))production mainly relies on the energy-intensive and environmentally unfriendly Haber-Bosch process.Such issue can be avoided by electrocatalytic N_(2) reduction which however suffers from limited current efficiency and NH3 yield.Herein,we demonstrate ambient NH_(3) production via electrochemical nitrite(NO_(2)^(-))reduction catalyzed by a CoP nanoarray on titanium mesh(CoP NA/TM).When tested in 0.1 M PBS(pH=7)containing 500 ppm N0_(2)^(-),such CoP NA/TM is capable of affording a large NH_(3) yield of 2,260.7±51.5μg·h^(-1)·cm^(-2) and a high Faradaic efficiency of 90.0±2.3%at-0.2 V vs.a reversible hydrogen electrode.Density functional theory calculations reveal that the potential-determining step for NO_(2)^(-)reduction over CoP(112)is*NO2→*NO_(2)H.

FeOOH quantum dots decorated graphene sheet:An efficient electrocatalyst for ambient N2 reduction

Electrochemical N2 reduction offers a promising alternative to the Haber-Bosch process for sustainable NH3 synthesis at ambient conditions,but it needs efficient catalysts for the N2 reduction reaction(NRR).Here,we report that FeOOH quantum dots decorated graphene sheet acts as a superior catalyst toward enhanced electrocatalytic N2 reduction to NH3 under ambient conditions.In 0.1 M LiClO4,this hybrid attains a large NH3 yield rate and a high Faradaic efficiency of 27.3µg·h^−1·mg−1cat.and 14.6%at−0.4 V vs.reversible hydrogen electrode,respectively,rivalling the current efficiency of all Fe-based NRR electrocatalysts in aqueous media.It also shows strong durability during the electrolytic process.

N-doped carbon nanotubes supported CoSe_(2) nanoparticles:A highly efficient and stable catalyst for H_(2)O_(2) electrosynthesis in acidic media

Electrocatalytic oxygen reduction reaction(ORR)provides an attractive alternative to anthraquinone process for H_(2)O_(2) synthesis.Rational design of earth-abundant electrocatalysts for H_(2)O_(2) synthesis via a two-electron ORR process in acids is attractive but still:very challenging.In this work,we report that nitrogen-doped carbon nanotubes as a multi-functional support for CoSe2 nanoparticles not only keep CoSe_(2) nanoparticles well dispersed but alter the crystal structure,which in turn improves the overall catalYtic behaviors and thereby renders high O_(2)-to-H_(2)O_(2) conversion efficiency.In 0.1 M HClO_(4),such CoSe_(2)@NCNTs hybrid delivers a high H_(2)O_(2) selectivity of 93.2% and a large H_(2)0_(2) yield rate of 172 ppm·h^(-1) with excellent durability up to 24 h.Moreover,CoSe_(2)@NCNTs performs effectively for organic dye degradation via electro-Fenton process.

N, O-doped carbon foam as metal-free electrocatalyst for efficient hydrogen production from seawater

Seawater electrolysis is the most promising technology for large scale hydrogen production due to the abundance and low cost of seawater in nature.However,compared with the traditional freshwater electrolysis,the issues of electrode poisoning and corrosion will occur during the seawater electrolysis process,and active and stable electrocatalysts for the hydrogen evolution reaction(HER)are thus highly desired.In this work,N,O-doped carbon foam in-situ derived from commercial melamine foam is proposed as a high-active metal-free HER electrocatalyst for seawater splitting.In acidic seawater,our catalyst shows high hydrogen generation performance with small overpotential of 161 mV at 10 mA·cm^(−2),a low Tafel slop of 97.5 mV·dec^(−1),and outstanding stability.

Enhanced N_(2)-to-NH_(3)conversion efficiency on Cu3P nanoribbon electrocatalyst

Ambient electroreduction of nitrogen(N_(2))is considered as a green and feasible approach for ammonia(NH_(3))synthesis,which urgently demands for efficient electrocatalyst.Morphology has close relationship with catalytic activity of heterogeneous catalysts.Nanoribbon is attractive nanostructure,which possesses the flexibility of one-dimensional nanomaterials,the large surface area of two-dimensional nanomaterials,and lateral size confinement effects.In this work,Cu_(3)P nanoribbon is proposed as a highly efficient electrocatalyst for N_(2)-to-NH_(3)conversion under benign conditions.When measured in N_(2)-saturated 0.1 M HCl,such Cu_(3)P nanoribbon achieves high performance with an excellent Faradaic efficiency as high as 37.8%and a large yield of 18.9μg·h^(−1)·mgcat.−1 at−0.2 V.It also demonstrates outstanding stability in long-term electrolysis test at least for 45 h.

Recent advances in nanostructured heterogeneous catalysts for N-cycle electrocatalysis

To restore the natural nitrogen cycle(N-cycle),artificial N-cycle electrocatalysis with flexibility,sustainability,and compatibility can convert intermittent renewable energy(e.g.,wind)to harmful or value-added chemicals with minimal carbon emissions.The background of such N-cycles,such as nitrogen fixation,ammonia oxidation,and nitrate reduction,is briefly introduced here.The discussion of emerging nanostructures in various conversion reactions is focused on the architecture/compositional design,electrochemical performances,reaction mechanisms,and instructive tests.Energy device advancements for achieving more functions as well as in situ/operando characterizations toward understanding key steps are also highlighted.Furthermore,some recently proposed reactions as well as less discussed C-N coupling reactions are also summarized.We classify inorganic nitrogen sources that convert to each other under an applied voltage into three types,namely,abundant nitrogen,toxic nitrate(nitrite),and nitrogen oxides,and useful compounds such as ammonia,hydrazine,and hydroxylamine,with the goal of providing more critical insights into strategies to facilitate the development of our circular nitrogen economy.

Benzoate anions-intercalated NiFe-layered double hydroxide nanosheet array with enhanced stability for electrochemical seawater oxidation

Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy,but detrimental chlorine species(i.e.,chloride and hypochlorite)cause severe corrosion at the anode.Here,we report our recent finding that benzoate anions-intercalated NiFe-layered double hydroxide nanosheet on carbon cloth(BZ-NiFe-LDH/CC)behaves as a highly efficient and durable monolithic catalyst for alkaline seawater oxidation,affords enlarged interlayer spacing of LDH,inhibits chlorine(electro)chemistry,and alleviates local pH drop of the electrode.It only needs an overpotential of 320 mV to reach a current density of 500 mA·cm^(−2)in 1 M KOH.In contrast to the fast activity decay of NiFe-LDH/CC counterpart during long-term electrolysis,BZ-NiFe-LDH/CC achieves stable 100-h electrolysis at an industrial-level current density of 500 mA·cm^(−2)in alkaline seawater.Operando Raman spectroscopy studies further identify structural changes of disorderedδ(NiIII-O)during the seawater oxidation process.

CeO_(2) nanoparticles with oxygen vacancies decorated N-doped carbon nanorods:A highly efficient catalyst for nitrate electroreduction to ammonia

Electrocatalytic nitrate reduction reaction(NO_(3)−RR)emerges as a highly efficient approach toward ammonia synthesis and degrading NO_(3)−contaminant.In our study,CeO_(2) nanoparticles with oxygen vacancies(VO)decorated N-doped carbon nanorods on graphite paper(CeO_(2)−x@NC/GP)were demonstrated as a highly efficient NO_(3)−RR electrocatalyst.The CeO_(2)−x@NC/GP catalyst manifests a significant NH_(3 )yield up to 712.75μmol·h^(−1)·cm^(−2) at−0.8 V vs.reversible hydrogen electrode(RHE)and remarkable Faradaic efficiency of 92.93%at−0.5 V vs.RHE under alkaline conditions,with excellent durability.Additionally,an assembled Zn-NO_(3)−battery with CeO_(2)−x@NC/GP as cathode accomplishes a high-power density of 3.44 mW·cm^(−2) and a large NH3 yield of 145.08μmol·h^(−1)·cm^(−2).Density functional theory results further expose the NO_(3)−reduction mechanism on CeO_(2)(111)surface with VO.

FeP nanorod array:A high-efficiency catalyst for electroreduction of NO to NH3 under ambient conditions

Sustainable mitigation of the continuously rising concentration of NO contaminants is among the most urgent issues of this century.Ambient electrocatalytic conversion of NO into useful NH_(3)offers an attractive path toward achieving sustainable NO abatement and NH_(3)production simultaneously.However,its efficiency is challenged by the intense competition from hydrogen evolution reaction and relatively high energy barriers of NO activation.It is thus highly desirable to explore active electrocatalyst for NO reduction reaction and investigate the mechanisms on relevant surfaces.Herein,we introduce an FeP nanorod array on carbon cloth as a high-efficiency catalyst for NO electroreduction to NH3.In 0.2 M phosphate-buffered solution,this catalyst exhibits a low onset potential of-0.014 V.Moreover,it achieves a remarkable Faradaic efficiency of 88.49%and a large NH_(3)yield of 85.62μmol·h^(-1)cm^(-2),with durability for stable NO conversion over 12 h of electrolysis.The catalytic mechanism on FeP is investigated further by theoretical calculations.

Bi nanoparticles/carbon nanosheet composite:A high-efficiency electrocatalyst for NO reduction to NH_(3)

Electrochemical reduction of NO offers us an attractive alternative to traditional selective catalytic reduction process for harmful NO removal and simultaneous NH_(3)production,but it requires efficient electrocatalyst to enable the NO reduction reaction with high selectivity.Here,we report on the development of Bi nanoparticles/carbon nanosheet composite(Bi@C)for highly effective NO reduction electrocatalysis toward selective NH_(3)formation.Such Bi@C catalyst attains an impressive NH_(3)yield of 1,592.5μg·h^(−1)·mgcat.^(−1)and a high Faradaic efficiency as high as 93%in 0.1 M Na_(2)SO_(4)electrolyte.Additionally,it can be applied as efficient cathode materials for Zn–NO battery to reduce NO to NH_(3)with high electricity generation.